Review of Vehicle Engine Efficiency and Emissions 2018-01-0329
This review paper summarizes major and representative developments in vehicle emissions regulations, engine efficiency, and emission control from 2017. The paper starts with the key regulatory developments in the field, including newly proposed European LD (light duty) CO2 regulations (15 and 30% cuts in 2025 and 2030, respectively, from 2020 levels) and technical improvements of the Euro 6 RDE (real driving emissions) regulations. China finalized their NEV (new energy vehicle) mandates for 2019 and 2020. LD and HD (heavy duty) engine technology continues showing marked improvements in engine efficiency. Key developments are summarized for gasoline and diesel engines to meet both the emerging criteria and greenhouse gas regulations. Several LD gasoline concepts are achieving 10-15% and some up to 35% reductions relative to GDI (gasoline direct injection) engines of today. Projections indicate tight CO2 regulations will require some degree of hybridization and/or high-performing gasoline and diesel engines. Scoping work on HD engines is reported on achieving 55% BTE (break thermal efficiency) using methods that can reasonably be commercialized. Lean NOx control technologies are summarized, including SCR (selective catalytic reduction), NOx adsorbers, and systems. Fundamentals of the SCR reaction are explored at the atomistic level. Diesel particulate filter (DPF) work has been focused on structure-performance relationships and ash behavior. Research oxidation catalysts are approaching 90% efficiency for hydrocarbon and CO oxidation at 160-190 °C. Gasoline particulates are a major topic in emissions control. The paper provides a broad overview of various factors that can impact emissions. The impact of fuel composition and application is summarized. Gasoline particulate filter durability and ash loading is better understood. Finally, the paper discusses some key developments in three-way catalysts, with improved understanding of low temperature performance. Advances in lean-burn gasoline emissions control from a few labs are also summarized.